Conventionally, in order to reduce nitrogen oxides (NOx) contained in exhaust gas from a marine engine, there are known exhaust gas purification devices configured to reduce NOx into nitrogen and water using a selective catalytic reduction NOx catalyst (SCR catalyst) and a reducing agent. For example, some of such devices are configured to generate ammonia from urea water sprayed into high-temperature exhaust gas and to reduce NOx into nitrogen and water on the NOx catalyst.
In regard to these exhaust gas purification devices, there has been known a device provided with a mixer configured to mix the exhaust gas with the reducing agent in order to enhance the efficiency of the reduction process on the NOx catalyst (for example, see Patent Literature 1 (PTL1)). In this exhaust gas purification device, the exhaust gas forcedly mixed with the reducing agent by the mixer is supplied to the NOx catalyst, thereby to enhance the efficiency of the reduction process of the exhaust gas.